The present invention relates to a process for perforating in oil wells, more particularly, to a process for continuously perforating at a predetermined place in a wellbore and an apparatus used for the same.
Wellbores drilled through earth formations for extracting oil and gas are typically completed by coaxially inserting a steel pipe (a casing) into the wellbore. Perforations are made by detonating charges through the casing and a cement ring outside thereof into the formation to create channels, which allows oil and gas to enter the wellbore.
There have been various perforating devices in prior art such as a jet perforator, a bullet perforator, and a laser perforator. A test has shown a hole perforated on the ceramic by a perforator in the art can reach a maximum depth of 967.74 mm and a maximum diameter of 28.45 mm. It is obvious that the foregoing perforators are not ideal for those wellbores in a poor condition of the formation.
An object of the invention is to provide a process for perforating in a wellbore to overcome the shortcomings in prior art. The process according to the invention comprises the following steps of: determining a location to be perforated in the wellbore proximate an oil formation; placing an apparatus comprising a plurality of charges to the location in the wellbore; and continuously conducting perforation at the location with the charges in the apparatus.
Another object of the invention is to provide an apparatus for continuously perforating in a wellbore. The apparatus according to the present invention comprises i) transmitting system comprising a gun housing including a plurality of chambers arranged from top to bottom with an identical distance between each two adjacent chambers, each chamber comprising a charge; and a plurality of initiators positioned within the gun housing and connected to the charges, respectively; a plurality of first contacts positioned on the outer portion of the gun housing and connected to the initiators, respectively, ii) positioning system comprising a base; a fluid pressure fastener mounted under said base for fixing the positioning system to the wellbore; and a sliding rail connected to the base, on which the transmitting system moves up and down, and iii) controlling system comprising a string connected to the gun housing; a second contact positioned on the upper portion of the sliding rail and connected to a power; a first cable connected to the initiator for controlling the detonation of the charge; and a second cable connected to the fluid pressure fastener, wherein when the transmitting system moves down along the sliding rail, the first contacts contact the second contact consecutively to initiate the charges.